ISSN:
0947-3440
Schlagwort(e):
Donor
;
acceptor complexes
;
Structures
;
Effects of H bridge networks in lattice layers
;
Chemistry
;
Organic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Interaction in Crystals, 94. - Donor/Acceptor complexes between Hydroquinone, Pyrene, Perylene, and N, N,N′,N′-Tetramethylbenzidine with 1,2,4,5-Tetracyanobenzene or Tetracyanohydroquinone: Structures with and without H Bridge NetworksDonor/acceptor complexes {D⃛A}∞ can be designed to crystallize in mixed stacks. Due to interplanar ring distances of double π van der Waals radii (340 pm), however, no significant structure changes are observed relative to those of their components. Therefore, it has been attempted to planarize the herringbone patterns of the crystal lattice by additional H bridge networks in order to increase the π interactions between the donor and acceptor rings. The following structural effects are observed: (i) Relative to the complex {perylene⃛1,2,4,5-tetracyanobenzene}∞, the planarization of the herringbone pattern by the H bridge network in {pyrene⃛2,3,5,6-tetracyanohydroquinone}∞ and {perylene⃛tetracyanohydroquinone(OH2)2}∞ shortens the layer distance from 345 to 340 pm. Nevertheless, still no significant structural changes due to π electron polarization become apparent. (ii) Despite of identical crystallization conditions from acetic acid solution for both pyrene and perylene inclusion compounds, only the more spacious perylene stretches the H bridges of tetracyanohydroquinone (OH⃛N≡C)2 by hydrate water inclusion (OH⃛OH2⃛N≡C)2 from 265 to 555 pm. (iii) In the complex {hydroquinone⃛1,2,4,5-tetracyanobenzene}∞ the phenolic OH substituents generate an extensive H bridge network within the mixed-staple layers, in which each hydroquinone is surrounded by four tetracyanobenzenes via both strong (OH⃛N≡C) and weak (CH⃛OH) contacts. (iv) In the complex {(tetracyanohydroquinone-)2⃛(N, N,N′,N′-tetramethylbenzidinium(H2+)(OH2)2} an additional proton transfer turns the hydroquinone anion into the donor and the doubly protonated benzidinium dication into the acceptor. - Additional UV/Vis spectroscopic investigations prove long-wavelength charge transfer bands between 11200 and 19000 cm-1, which are shifted relative to the component absorptions by partly up to 1.5 eV (!) and can be approximated by AM1/CI or PM3/CI calculations. The missing structural changes in the ground state of the complexes {D⃛A∞} demonstrate therefore, that the electron transfer from donor to acceptor is largely initiated on excitation.
Zusätzliches Material:
6 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/jlac.199619961129
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